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1.G.11 The Poxvirus Cell Entry Protein Complex (PEP-C) Family

For many viruses, one or two proteins enable cell binding, membrane fusion and entry. The large number of proteins employed by poxviruses may be related to their ability to infect a wide range of cells (Moss, 2012). There are two main infectious forms of vaccinia virus, the prototype poxvirus: the mature virion (MV), which has a single membrane, and the extracellular enveloped virion (EV), which has an additional outer membrane that is disrupted prior to fusion. Four viral proteins associated with the MV membrane facilitate attachment by binding to glycosaminoglycans or laminin on the cell surface, whereas EV attachment proteins have not yet been identified. Entry can occur at the plasma membrane or in acidified endosomes following macropinocytosis and involves actin dynamics and cell signaling. Regardless of the pathway or whether the MV or EV mediates infection, fusion is dependent on 11 to 12 non-glycosylated, transmembrane proteins ranging in size from 4- to 43-kDa that are associated in a complex. These proteins are conserved in poxviruses making it likely that a common entry mechanism exists. Biochemical studies support a two-step process in which lipid mixing of viral and cellular membranes is followed by pore expansion and core penetration (Moss, 2012).

References associated with 1.G.11 family:

Moss, B. (2012). Poxvirus Cell Entry: How Many Proteins Does it Take? Viruses 4: 688-707. 22754644
Tak, A.I., J.L. Americo, U.S. Diesterbeck, and B. Moss. (2021). Loss of the vaccinia virus 35-amino acid hydrophobic O3 protein is partially compensated by mutations in the transmembrane domains of other entry proteins. J. Virol. [Epub: Ahead of Print] 33504600
Takeo K., Watanabe N., Tomita T. and Iwatsubo T. (2012). Contribution of the gamma-secretase subunits to the formation of catalytic pore of presenilin 1 protein. J Biol Chem. 287(31):25834-43. 22689582